From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: Re: [PATCH v2 3/9] provide in-kernel ioapic Date: Fri, 9 Oct 2009 11:32:25 -0300 Message-ID: <20091009143225.GV8092@mothafucka.localdomain> References: <1254953315-5761-1-git-send-email-glommer@redhat.com> <1254953315-5761-2-git-send-email-glommer@redhat.com> <1254953315-5761-3-git-send-email-glommer@redhat.com> <1254953315-5761-4-git-send-email-glommer@redhat.com> <4ACDEDEC.60706@us.ibm.com> <4ACDEF03.6010406@redhat.com> <20091008160726.GD29691@shareable.org> <4ACE10B5.3080509@redhat.com> <20091008162248.GK16702@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Anthony Liguori , Avi Kivity , kvm-devel , qemu-devel@nongnu.org To: Gleb Natapov Return-path: Content-Disposition: inline In-Reply-To: <20091008162248.GK16702@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org List-Id: kvm.vger.kernel.org On Thu, Oct 08, 2009 at 06:22:48PM +0200, Gleb Natapov wrote: > On Thu, Oct 08, 2009 at 06:17:57PM +0200, Avi Kivity wrote: > > On 10/08/2009 06:07 PM, Jamie Lokier wrote: > > >Haven't we already confirmed that it *isn't* just an ioapic accelerator > > >because you can't migrate between in-kernel iopic and qemu's ioapic? > > > > We haven't confirmed it. Both implement the same spec, and if you > > can't migrate between them, one of them has a bug (for example, qemu > > ioapic doesn't implement polarity - but it's still just a bug). > > > Are you saying that HW spec (that only describes software visible behavior) > completely defines implementation? No other internal state is needed > that may be done differently by different implementations? Most specifications leaves a lot as implementation specific. It's not hard to imagine a case in which both devices will follow the spec correctly, (no bugs involved), and yet differ in the implementation. From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MwGWJ-0007Z9-1N for qemu-devel@nongnu.org; Fri, 09 Oct 2009 10:32:35 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MwGWE-0007XG-7X for qemu-devel@nongnu.org; Fri, 09 Oct 2009 10:32:34 -0400 Received: from [199.232.76.173] (port=34609 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MwGWE-0007XD-0t for qemu-devel@nongnu.org; Fri, 09 Oct 2009 10:32:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44108) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1MwGWD-0005lv-LV for qemu-devel@nongnu.org; Fri, 09 Oct 2009 10:32:29 -0400 Date: Fri, 9 Oct 2009 11:32:25 -0300 From: Glauber Costa Subject: Re: [Qemu-devel] Re: [PATCH v2 3/9] provide in-kernel ioapic Message-ID: <20091009143225.GV8092@mothafucka.localdomain> References: <1254953315-5761-1-git-send-email-glommer@redhat.com> <1254953315-5761-2-git-send-email-glommer@redhat.com> <1254953315-5761-3-git-send-email-glommer@redhat.com> <1254953315-5761-4-git-send-email-glommer@redhat.com> <4ACDEDEC.60706@us.ibm.com> <4ACDEF03.6010406@redhat.com> <20091008160726.GD29691@shareable.org> <4ACE10B5.3080509@redhat.com> <20091008162248.GK16702@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091008162248.GK16702@redhat.com> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gleb Natapov Cc: Anthony Liguori , Avi Kivity , kvm-devel , qemu-devel@nongnu.org On Thu, Oct 08, 2009 at 06:22:48PM +0200, Gleb Natapov wrote: > On Thu, Oct 08, 2009 at 06:17:57PM +0200, Avi Kivity wrote: > > On 10/08/2009 06:07 PM, Jamie Lokier wrote: > > >Haven't we already confirmed that it *isn't* just an ioapic accelerator > > >because you can't migrate between in-kernel iopic and qemu's ioapic? > > > > We haven't confirmed it. Both implement the same spec, and if you > > can't migrate between them, one of them has a bug (for example, qemu > > ioapic doesn't implement polarity - but it's still just a bug). > > > Are you saying that HW spec (that only describes software visible behavior) > completely defines implementation? No other internal state is needed > that may be done differently by different implementations? Most specifications leaves a lot as implementation specific. It's not hard to imagine a case in which both devices will follow the spec correctly, (no bugs involved), and yet differ in the implementation.